Various methods and apparatus for packaging articles in plastic bags are available today or have been suggested in the past. In one packaging method, the bags form part of a continuous plastic web, each bag being connected to a contiguous bag along a line of weakness. Typically, the bags define an opening on one face through which the bag is loaded.
In early bagging machines, an operator manually loaded the product into the bag and the bag was pulled downwardly to position the next bag at the loading station. The loaded bag was then manually severed from the web.
Machines and methods for automatically loading a chain of interconnected plastic bags have been developed or have been suggested by the prior art. In general, these machines include a mechanism for sequentially feeding a lead bag to a loading station; a mechanism for expanding the mouth of the bag and maintaining it in the expanded condition during a loading operation; and, a mechanism for severing the loaded bag from the chain. After the loaded bag is severed, the packaging sequence begins again with the next bag.
The individual bags are usually joined to the chain or web by a line of weakness generally formed by a plurality of perforations. After the bag is loaded, it is severed from the web along the perforations. Various mechanisms for automatically severing the loaded bag from the web have been developed or suggested. In one known method, the separation along the perforations is initiated by a projection that begins the tearing action near the center of the line of weakness. Severance of the bag then commences at the center of the line of weakness and proceeds outwardly toward the marginal edges. An example of such a mechanism is shown in U.S. Pat. No. 3,477,196, which is owned by the present assignee.
An alternate method for severing a loaded bag from a web is disclosed in U.S. Pat. No. 4,202,153 which is also owned by the present assignee. In the method and apparatus shown in this patent, a transversely movable product carrier enters an opened bag, positioned horizontally, and simultaneously loads the bag and severs it from the web. Severance is achieved by overdriving the product carrier so that it engages the bottom of the loaded bag and drives it away from the web while the remainder of the web is held stationary, thus tearing the loaded bag from the web. In the disclosed apparatus, the perforation breakage commences near the marginal edges of the web and advances inwardly from the marginal edges toward the center. Because the perforations are broken serially, the force needed to sever the container is less than that required if the perforations were broken simultaneously.
In U.S. Pat. No. 3,815,318 (also owned by the present assignee), a packaging method and apparatus is disclosed which illustrates another apparatus for severing a loaded bag along a line of weakness. In this apparatus, the tearing action is produced by a pivoting mechanism which engages a loaded bag and pivots the bag about an axis located near one marginal edge while the web is held stationary. The tearing action then commences at a remote marginal portion and advances towards the edge of the bag that is located at or near the pivot axis.
A method and apparatus for simultaneously filling two adjacent bags have also been suggested in the past. In particular, U.S. Pat. No. 4,041,846, owned by the present assignee, illustrates detachable, interconnected container strips and a method of making these strips. The strips are connected in a side-by-side relationship in order to define adjacent bags. In this patent, however, the adjacent bags are attached and cannot move independently of each other prior to filling. After filling, the attached side-by-side bags are separated.
A machine described in U.S. Pat. No. 4,899,520 entitled "Packaging Apparatus and Method" also includes an ability to use two chains of interconnected bags while packaging. After bags are loaded, they are sealed with a heater bar which melts adjacent plastic plys to fuse them together. During the sealing operation, the weight of the bag's contents and bag separation forces are isolated from the region of the seal by spring biased grippers that are moved into engagement with a bag by a clamping sub-assembly that also brings the bag into contact with the sealer bar.
U.S. Pat. No. Re. 32,963 to Lerner et al. discloses a packaging machine for loading a chain of interconnected bags. A gripper assembly clamps the bag to be loaded to a funnel mechanism. An incremental reversing mechanism retracts the web of bags after the endmost bag is loaded to sever the bag from the web along a line of weakness.